The lang function returns true or false depending on whether
the language of the context node as specified by
xml:lang
attributes is the same as or is a sublanguage
of the language specified by the argument string. The language of the
context node is determined by the value of the xml:lang
attribute on the context node, or, if the context node has no
xml:lang
attribute, by the value of the
xml:lang
attribute on the nearest ancestor of the
context node that has an xml:lang
attribute. If there
is no such attribute, then lang
returns false. If there is such an attribute, then lang returns true if the attribute
value is equal to the argument ignoring case, or if there is some
suffix starting with -
such that the attribute value
is equal to the argument ignoring that suffix of the attribute value
and ignoring case. For example, lang("en")
would
return true if the context node is any of these five elements:
<para xml:lang="en"/>
<div xml:lang="en"><para/></div>
<para xml:lang="EN"/>
<para xml:lang="en-us"/>